In recent years, as an input detection device, attention has been paid to an input detection device with a touch detection function, which is so called touch panel, capable of detecting that an external object is close to (hereinafter, also in contact with) the device. A touch panel is mounted on a display apparatus such as a liquid crystal display apparatus or integrated with a liquid crystal display apparatus so as to be provided as a display apparatus with a touch detection function.
As the external object, a touch panel enabled to use, for example, a pen is known. By enabling the touch panel to use a pen, for example, a small region can be assigned or hand-written characters can be input. Various techniques to detect the touch by a pen are known. As one of the various techniques, an electromagnetic induction system is known. In the electromagnetic induction system, high accuracy and high handwriting pressure detection accuracy can be achieved, and a hovering detection function in a state in which an external object is separated from the touch panel surface can be also achieved, and therefore, the system is a leading technique as the technique to detect the touch by a pen.
A touch detection device capable of detecting a finger, etc., as the external object is known. In this case, an object to be detected is different from the pen, and therefore, a system different from the electromagnetic induction system is employed for the touch detection technique. For example, systems of detecting optical change, resistance value change, or electric field change, caused by the finger touch, etc., are cited. As the system of detecting the electric field change among these systems, for example, an electrostatic capacitive system utilizing a capacitance is cited. This electrostatic capacitive system has a relatively simple structure and less power consumption, and therefore, is used for a portable information terminal, etc.
The technique related to the touch panel of the electromagnetic induction system is described in, for example, Japanese Patent Application Laid-Open Publication No. H10-49301 (Patent Document 1).